Frangible port closure



0a. 2a, 1969 |.c.PosoNowsKl 3,414,630

FRANGIBLE PORT CLOSURE Filed June 4. 1968 ..L. Y E

United States Patent 3,474,630 FRANGIBLE PORT CLOSURE Ivo C. Pogonowski,Houston, Tex., assignor to Texaco Inc., New York, N.Y., a corporation ofDelaware Filed June 4, 1968, Ser. No. 734,342 Int. Cl. E021) 17/00,21/00; F16 15/06 U.S. Cl. 6146.5 15 Claims ABSTRACT OF THE DISCLOSUREThe invention relates to a frangible closure for an aperture formed in afluid tight bulkhead for use within an underwater structure. It relatesparticularly to a water tight closure adapted to form a temporary sealacross a bulkhead. The closure is adequate to maintain a water tightcondition, under pressure, and yet fragile enough to fracture whenforcibly contacted by a conductor pipe or similar member being passedthrough the aperture, whereby the pipe will be sealably engaged withsaid bulkhead.

BACKGROUND OF THE INVENTION In many structures adapted for underwaterusage such as offshore marine drilling platforms, platform supports, andthe like, the latter are frequently adapted to be at least partiallybuoyant. The feature of buoyancy entails several distinct advantages.First, the support structure might be floated to a desired position andthereafter lowered as required by controlled flooding of scalablecompartments. Secondly, the scalable compartments within the structureconstituted a convenient storage facility for crude oil removed from theground.

An example of this type of structure is often found in marine platformssupported on a single column. -In such structures, the column extendsfrom the ocean floor to a position above the water surface. The columnthereby forms not only a support for the equipment deck, but also aprotective jacket about internally positioned conductors which extendlongitudinally of the column and are adapted to receive the normalcomplement of producing and drilling pipes.

The number of such conductors actually used is variable depending on theproductivity of the particular location. In the instance of a relativelylarge support casing, the conductors might number as many as 25 or 30,discretely positionel through the casing.

To facilitate the placing of a marine platform, whether of the single,or multiple support leg type, in a body of Water, it is expedient toinsert the pipe conductors subsequent to the casing being set in anupright, supporting position. However, to maintain the controlledbuoyancy necessary to effect the positioning of such a casing orplatform support, the column must of necessity embody a number ofcontrolled buoyancy tanks. In the instance of a relatively simplestructure comprising basically a single elongated support column, thelatter is normally provided with transversely placed and longitudinallyspaced bulkheads, adjacent of which bulkheads define evacuable orbuoyancy controllable chambers.

To maintain the variable buoyant capacity of these respective chambers,the transverse bulkheads are initially made fluid tight and yet adaptedto subsequently receive the one or more conductors passinglongitudinally of the casing. However in order that the oil storingfeature of the column might be retained, the respective chambers, whichare transversed by the conductors, must similarly be sealed off betweenbulkheads.

-For relatively shallow water operation it is a simple matter to provideeach casing bulkhead with a number of openings which will subsequentlyreceive a conductor pipe. These openings are initially closed to sealthe casing,

'ice

which closure means normally comprises a welded or bolted into placecover disposed across each individual opening. To receive theconductors, the respective closures are usually removed by a diver.After the conductors are lowered through the aligned bulkhead aperturesthe conductors are Welded into place.

While this procedure is feasible for relatively shallow water adapted todiver operations, in the instance of deep water installations theproblem is somewhat compounded. Not only is the initially installationcost greatly increased by the use of divers for waters in depths ofapproximately 300 to 1,000 feet, but such an operation is time consumingand uneconomical.

For example to install a plurality of conductors in a relatively deepwater location, it is necessary for the diver to not only remove thetemporary closure at each bulkhead, but also to subsequently weld theconductor pipe to the bulkhead thereby forming a peripheral water tightseal.

It is therefore an object of the present invention to provide a novelmarine platform support adapted to receive at least one, and preferablya plurality of longitudinally positioned conductors or similar pipes.Another object is to provide a support column of the type describedparticularly adapted to receive one or more conductor pipeslongitudinally therethrough subsequent to the column being positioneduprightly in an offshore location. A further object is to provide afrangible closure adapted to sealably close an under water aperturesubsequent to insertion of conductor members therethrough such that saidmembers will be sealably positioned. A still further object is toprovide an arrangement whereby one or more pipe conductors may be setand positioned in a marine platform support column subsequent to thelatter being set into working position.

DESCRIPTION OF THE DRAWINGS In the drawings, FIGURE 1 comprises a sideelevation illustrating an offshore marine platform set in position on anocean floor. FIGURE 2 is an enlarged segmentary veiw in cross sectionshowing a portion of the upright casing of FIGURE 1. FIGURE 3 is a viewtaken along line 33 in FIGURE 2. FIGURE 4 is an enlarged segmentary viewin cross section of one embodiment of the closure assembly. FIGURES 5 to8 are views similar to FIGURE 4 showing alternate embodiments of theclosure assembly.

In brief, the basic objectives of the invention are achieved by theprovision of an elongated, upright marine platform support which isadapted to receive a plurality of conductor casings. The support, orcolumn member is provided with a plurality of longitudinally spacedwater tight bulkheads, each of which includes apertures formed thereinand disposed in substantial longitudinal alignment with similarapertures in the other bulkheads. The number of apertures so formed isusually indefinite since the ultimate productivity of the well willdetermine the number of conductors to be subsequently set in a column,which productivity normally is unknown at the time the platform islowered into position. Initially, each bulkhead aperture is providedwith a frangible closure to fluid tightly seal the opening, whichclosure however may be readily shattered by a conductor pipe forcefullypassed therethrough. The closure assembly serves the further purpose ofguiding the downwardly moving conductor pipe as the latter approacheseach bulkhead so that the conductor will most effectively strike thefrangible portion of the closure, and be sealed to the bulkhead.

Referring to FIGURE 1, a marine platform support member of the typecontemplated is shown and includes elongated casing 10 formed of acylindrical water tight column or casing of relatively large diameter.The upper end of the column supports a drill platform or deck 11 abovethe water surface. The deck accommodates a drill table, derrick, andaccessory equipment normally associated with the drilling and producingfacilities of an offshore well site. While the present description anddrawings are directed specifically to a structure utilizing but a singlecolumn for supporting a platform, it is understood that a plurality ofsuch supports could as readily be utilized depending on the particularcircumstance and design of the unit. Further, although the presentdescription relates to a support column 10 adapted to accommodate butfour conductors, the actual number which might be practically receivedis a function of the design of the column which in turn relates to thedepth of the Water and the weight of the supported structure.

The lower end of upstanding casing 10 is provided with a supporting baseas representatively shown in FIGURE 1, comprising a plurality of footingmembers 16 and 17. A cross member 20, together with legs 18 and 19extend from the respective base members upwardly connecting to thecolumn to provide lateral support to the casing 10.

As shown in FIGURE 2, casing 10 includes an elongated cylindrical memberfabricated of individual sections of steel pipe or casing. A pluralityof bulkheads 12 and 13 are peripherally welded to the casing inner wall,thereby forming between adjacent of said bulkheads, a buoyant chamber.The respective chambers are controlled by a suitable pipe and valvingsystem not presently shown, but which is communicated with sources ofoil and water and air. Such piping serves the purpose of regulating thecontent of the respective chambers whether for controlling the buoyancyof the column or merely for storing oil.

Referring again to FIGURE 2, conductor pipes 21 and 22 depend downwardlyfrom deck 11 and are normally imbedded for a short distance into theocean floor by jetting, driving, or other appropriate method. Eachconductor bulkhead, 12 for example, is provided with a plurality ofapertures 15 and 15' disposed in axial alignment, which apertures inadjacent bulkheads being of a size compatible with the downwardlypassing conductor pipe.

A closure assembly 23 is positioned at each bulkhead aperture and isadapted to slideably receive, and engage a conductor outer wall to forman annular fluid tight seal with the conductor after the latter has beenlowered into place.

Referring to FIGURE 4, closure assembly 23, in its simplest form isshown, and comprises basically a frangible plate or disc 26 disposedacross opening 27, having the disc edges overlying at least a portion ofthe openings rim. A ring seal or gasket 29 is compressibly deformedbetween bulkhead 28 and frangible plate 26 to form an annular liquidtight seal prior to insertion of a conductor pipe. A conductor guide 32comprises an inwardly tapered conical section which is larger at one endthan the diameter of the conductor and tapers to a constricted openingterminating adjacent the frangible plate. In such position, a conductorwill be received in conductor guide 32 and while being lowered isdirected to its proper position for fracturing frangible plate 26.

As seen in FIGURE 8, seal ring 29 is deformed against the wall ofconductor 21 and maintains the water tight integrity of bulkhead 12 bothprior to, and subsequent to insertion of a conductor. Said seal ring 29includes a center opening of a size slightly smaller in diameter thanthe conductor 21 outside diameter such that as the latter fracturesfrangible plate 26, it will engage the seal ring center opening in asliding, although liquid tight annular seal. Thus as a conductor 21 isprogressively passed through each of the bulkhead apertures, thefrangible closures in each location will be shattered. Further, theindividual fluid tight integrity of each buoyant compartment will beassured by immediate engagement of the conductor outer wall with a sealring center opening.

FIGURE illustrates an alternate embodiment of the above describedclosure assembly wherein frangible plate 34 is sealably fixed to theunderside of bulkhead 36 with a compressible seal ring 37 deformedbetween said respective plate and bulkhead to form the desired annularseal both with the bulkhead and with the conductor. The upper side ofplate 36 is provided with conductor guide 37 which includes a flange 38peripherally welded at a Water tight seam 40 to the bulkhead. Guidepassage 39 is formed of inwardly tapered Walls as herein noted, whichreceive a downwardly passing conductor and directs the same toward thebulkhead aperture 41.

FIGURE 6 illustrates a further embodiment of the novel, frangibleclosure assembly wherein bulkhead 42 is provided with an aperture 43.Frangible plate 44 is positioned across opening 43 overlying the rim ofthe latter. The plate 44 under surface is provided with a circularfracture groove or notch 46 which in effect weakens the structure of theplate such that upon contact with the downwardly moving conductor 47,said plate will fracture at the weakened portion defined by the fracturenotch.

Seal ring 48 is compressibly deformed against the upper surface of thefrangible plate 44 to form an annular water tight seal both with thebulkhead, and with the subsequently positioned conductor 47. Plate 44and gasket 48 are maintained in position by a retainer 49 comprising aflange 51 from which depends a shoulder 52, the inner edge of whichdefines a central opening adapted to slideably receive conductor 47.Shoulder 52 is spaced from the surface of bulkhead 42 to define acircular channel in which the respective frangible plate and seal ringare retained. A conductor guide portion 53 depends outwardly fromshoulder 52 and is incorporated therewith. As in the instance of theembodiment shown in FIGURE 4, the conductor guide 53 includes primarilya conical passage having an opening to receive the conductor 47, andbeing tapered to a constricted passage slightly larger than the diameterof said conductor.

In the instance of an elongated column 10 disposed in relatively deepwater, it is usually necessary to utilize a series of bulkheads both forlaterally bracing the column, and for directing the respectiveconductors. The fracturing of a number of frangible closures couldconstitute a problem of accumulation particularly in the in stance wherea relatively large number of conductors are to pass through a singlecasing. As shown in FIGURE 6, therefore frangible plate 44 may beprovided with a retainer such as a rivet or bracket 54 adapted toreceive a restraining chain or similar line 57. The remote end of chain57 is connected to a similar bracket welded to the underside of bulkhead42.

' As frangible plate 44 is fractured by the downwardly passing conductor47, the center of the plate is sheared at the notch 46. The separatedcenter portion then swings to one side, suspended by chain 57 at aposition adjacent to conductor 47. The retention of the center portionsof the various fractured plates avoids accumulation of said plates atthe next lower bulkhead which accumulation might tend to deflect aconductor or provoke a faulty positioning of the conductor on said nextlower bulkhead.

FIGURE 7 illustrates still another embodiment of the novel closurecomprising essentially a frangible plate assembly 61 which is maintainedacross aperture 62 by retainer 63. The plate assembly includes frangileplate 64 having a relatively Wide flange 66 with inwardly spaced,upstanding hub or rim 67. The latter forms a confining wall adapted torestrain inward contraction of the seal ring 68 which is deformedoutwardly by the hub prior to engaging the wall of conductor pipe 76. Asin the previously described embodiments of the closure member, aconductor guide 71 is carried on the casing bulkhead and so shaped tolead a downwardly passing conductor pipe into engagement with thefrangible plate 64.

In this arrangement, plate 64 is fabricated in such manner to facilitateits being positioned against bulkhead 72 by locating the plate assemblybetween the retainer lip 73 and the bulkhead surface. Thus, circular hub67 is topped by a curved crown 74 at the upper side for engaging thedownwardly moving conductor edge.

The function of hub 67 is two-fold. First, it maintains seal ring 68 ina retracted, prestressed position with the center opening stressed apartor deformed radially outwardly. The hub is thus provided with an outerdiameter approximately the diameter of downwardly passing conductor 76.As conductor 76 is directed by guide piece 71 into engagement with crown74, the hub will tend to shear through the thickness of flange 66thereby in effect shearing out the entire center section of thefrangible plate. To facilitate this severing action, a circular fracturenot 78 may be formed in the surface of the flange 66 immediatelyadjacent to the periphery of hub 67.

As the hub is dislodged and urged through the aperture 62 after beingsevered from the flange, seal ring 68 will release from its deformedposition and move outwardly to contact the downwardly passing conductorwall in a peripheral seal. The central opening in seal ring 68 is soformed to provide a suitable water tight, although sliding fit betweenthe seal edge and the conductor thereby assuring that as the latterbecomes fully positioned and stationary, the light peripheral seal ismaintained to sustain the condition of the respective buoyancy chambersare in condition then to function as buoyancy elements or as oil storagemeans. Plate 64 may be provided with a chain as mentioned with respectto the assembly shown in FIGURE 6 for retaining the center segment ofplate 64 when the latter has been dislodged from its position.

Plate assembly 61 is located across aperture 62 by retainer 63, the lip73 of which defines, with the bulkhead surface, a confining channel intowhich the entire plate assembly might readily be inserted prior toretainer 63 being welded to the surface of bulkhead 72. Retainer 63 ispreferably so welded to form a water tight peripheral joint about theretainer to again maintain the leak proof condition by the adjacentbuoyant chambers formed by the respective bulkheads.

The frangible plate which forms at least a part of the sealing member inthe presently described invention may be fabricated of a material bestadapted to the dual functions of both withsanding a fluid pressure indeep water, and shattering on impact. For example it has been found thatto withstand the water pressure at greatly sumerged depths to the pointof being fractured by a force of a downwardly moving conductor, certainglass or glass derivatives constitute a satisfactory plate material. Thethickness of the glass is of course dependent on the particular depth ofwater in which the column will be positioned. Another material suitableto the present application and similar to glass is a thermosettingplastic material such as Lucite. A desirable characteristic of thefrangible material of course is that it will sever readily from the mainbody of the plate and not tear as would be the case in the instance ofmost metallic closure members although certain thicknesses of suchmetallic members could produce the desired result.

In that the normal severance portion constitutes a circular area definedby the thickness of the casing wall, the frangible portion of theclosure may be limited. To withstand elevated water pressures then, theclosure may be reinforced across the center to avoid bending anddeflection stresses inherent in circular members subjected to staticpressure. Further, while a relatively simple circular gasket is adaptedto provide a fluid tight seal about the casing, said seal element mayassume a number of configurations to achieve the desired purpose.

With respect to the insertion of one or more elongated conductors into acasing as herein described, the casing is normally floated or barged toits deep water position without the conductors. The unit is then causedto adjust to a substantially upright attitude in the water by controlledflooding of buoyant chambers at the casing lower end. In said uprightposition, the casing is lowered to its its desired location with thelower end in contact with, or sunk at least partially into the oceanbottom. Following usual practice, it is understood that the casing wouldhave a suitable support base such as shown in FIGURE 1, or an equivalentarrangement for maintaining an upright posture. In such an anchoredcondition the conductor pipes are individually lowered into the casingfrom a derrick barge or from the supported deck 11, to engage and besealed to successive bulkheads.

The conductor, following standard practice, comprises end welded,suitably sized pipe lengths joined to form a continuous conductor havinga diameter appropriate to the diameter of the aperture in the respectivebulkheads. The weight of the conductor string is normally suflicientlygreat when lowered and guided onto a closure plate to break or shear thefrangible portion thereby permitting the conductor to slide through thebulkhead aperture and sealably engage the surrounding seal ring. Theconductor is then successively lowered for a similar engagement with theremaining bulkheads. In each instance, the frangible member is fracturedand the peripheral seal made with the conductor outer surface.

While we have described but one form of guide conductor which willsuitably bring the lower end of the conductor into engagement with theclosure plate, it is understood that other guide means might as well beemployed to achieve a similar function. Particularly at extreme waterdepths, the possibility exists of the column or the casing 10, inassuming a vertical attitude, might incorporate a degree of deflectionof the casing due to water pressure. In order therefore to properlyguide the conductor into engagement with the next lower frangible plate,additional intermediate guide members might be employed to properly leadthe conductor on its downward path.

Obviously many modifications and variations of the invention, ashereinafter set forth, may be made without departing from the spirit andscope thereof, and therefore, only such limitations should be imposed asare indicated in the appended claims.

I claim:

1. In a marine platform for an offshore oil producing installationincluding a casing normally at least partially submerged in an uprightposition and extending from the ocean bottom to the surface thereof, aplurality of bulkheads carried in said casing and spaced longitudinallythereof to define fluid tight buoyancy chambers therebetween, saidbulkheads including apertures disposed in substantial axial alignmentand adapted to sealably register at least one elongated conductor pipewhen the latter is passed longitudinally of said casing subsequent tosaid casing being disposed in an upright, partially submerged positionat a drilling site; and

sealing means carried on said plurality of bulkheads to maintain thefluid tight integrity thereof prior to, and subsequent to registrationof said at least one conductor pipe therethrough and including;

a closure member disposed in sealing relationship with each of saidapertures,

said closure member being formed at least in part of a frangiblematerial to permit fracture of said frangible portion when said closuremember is abuttingly engaged by the end of a conductor pipe being passedthrough said respective aligned apertures, and

seal means defining a peripheral fluid tight joint between saidconductor pipe and said bulkhead when said pipe is registered in saidapertures.

2. In a marine platform as defined in claim 1 wherein said closuremember includes a frangible portion adapted to being fractured and areinforcing portion cooperative with said frangible portion.

3. In a marine platform as defined in claim 1 wherein the frangibleportion of said closure member is formed of a material chosen from thegroup consisting of glass, ceramic, thermosetting plastic, and Wood.

4. In a marine platform as defined in claim 1 wherein said sealing meansincludes a gasket disposed intermediate said closure member and saidbulkhead, said gasket having a center opening slightly smaller than thediameter of the conductor pipe passed therethrough and being adapted toform an annular seal about the periphery of said pipe.

5. In a marine platform as defined in claim 1 including a guide meanscarried at the upper side of said closure member and having an openingto guidably receive the end of said conductor pipe for directing thelatter into engagement with said closure member.

6. In a marine platform as defined in claim 4 wherein said guide memberincludes a conical section having an enlarged open end greater than thediameter of said pipe, and tapering to a constricted portion disposedadjacent to said closure member the latter being characterized by adiameter slightly greater than the diameter of said conductor pipe.

7. In a marine platform as defined in claim 5 wherein said guide memberis positioned at the upper side of said bulkhead wherein said casing isin said upright position to receive said conductor pipe, and saidclosure member is sealably positioned at the lower side of the closuremember.

8. In a marine platform as defined in claim 5 wherein said guide memberincludes a flange having a shoulder spaced from said bulkhead anddefining an annular channel therebetween, said closure member beingdisposed within said annular channel and sealably engaging saidbulkhead, and a conical portion depending from said shoulder in adirection away from said bulkhead to receive said conductor pipe forguiding the latter into engagement with said closure member.

9. In a marine platform as defined in claim 8 including seal meanscompressibly retained intermediate said shoulder and said closure memberto define an annular liquid tight seal.

10. In a marine platform as defined in claim 1 wherein the frangibleportion of said closure member includes a groove formed into the surfacethereof adjacent to the rim of said aperture, and having a diameterslightly greater than the diameter of said conductor pipe to permitfracturing of said frangible closure.

11. In a marine platform as defined in claim 10 wherein said groove isformed in the underside of said frangible portion.

12. In a marine platform as defined in claim 10 wherein said groove isformed in the top side of said frangible portion.

13. In a marine platform as defined in claim 1 including connectingmeans having one end connected to said closure plate and the other endconnected to said bulkhead for supporting the fractured portion of saidclosure member after said conductor pipe has been passed therethrough.

14. In a marine platform as defined in claim 1, wherein said closuremember includes an upstanding circular rim formed on the surface thereofand having a diameter approximating the diameter of said conductor pipe,said seal means being disposed externally of said rim and being normallyoutwardly deformed into an open position by the latter, wherebyengagement of said conductor pipe end with said rim will cause thefrangible portion of said closure member to fracture, thereby releasingsaid deformed seal means for engaging the downwardly passing Wall ofsaid conductor pipe.

15. In a marine platform as defined in claim 14 including a circulargroove formed into the side of said closure member frangible portionopposite to said rim.

References Cited UNITED STATES PATENTS 2,771,747 11/1956 Rechtin 6l46.52,979,910 4/1961 Crake 6l46 JACOB SHAPIRO, Primary Examiner US. Cl. X.R.

